1. Field of the Invention
The present invention relates to novel Ru-sulfoxide complex catalysts, their preparation, their use in crosslinkable silicone compositions and also the silicone elastomers produced therefrom.
The addition of Si—H-functional compounds onto compounds having aliphatic unsaturated bonds, in particular C═C double bonds (hydrosilylation) has been known for a long time.
2. Description of the Related Art
Si-containing organic compounds, organosilanes and organopolysiloxanes can be prepared by hydrosilylation. Hydrosilylation is used, in particular, in the addition-crosslinking curing of organopolysiloxanes in the silicone industry, for example for the production of elastomers, impression-making compositions in the dental industry or antiadhesive coatings in the paper and films industry.
Platinum and compounds thereof are most frequently used as catalysts for the hydrosilylation reaction, with the platinum being used either in metallic form, as metal immobilized on an inorganic support, as a platinum salt or in the form of a soluble or insoluble platinum complex.
Up to now, the “Karstedt catalyst” which consists predominantly of a dimeric platinum-tetramethyldivinylsiloxane complex which can be described by the formula [Pt2(TMDVS)3] (TMDVS=tetramethyldivinyldisiloxane) and is known from U.S. Pat. No. 3,715,334 and U.S. Pat. No. 3,775,452 has been used for the majority of hydrosilylation reactions carried out in industry. The Karstedt catalyst is prepared from hexachloroplatinic acid H2PtCl6 which as an alcoholic solution is likewise frequently used as a hydrosilylation catalyst.
Since platinum is one of the most expensive noble metals, efforts have frequently been made to use other metals and compounds thereof as catalysts in hydrosilylation. Thus, the use of the other platinum group metals Pd, Rh, Ir, Ru in hydrosilylation is already known from the prior art. However, these have been described as alternatives to Pt mainly as catalysts for use in the case of specific substrates.
Thus, for example, US 2004/0092759 A1 and U.S. Pat. No. 5,559,264 describe Ru catalysts such as RuCl3, RuBr3, Ru(acac)3, Ru/C, Ru3(CO)12, [RuCl2(CO)3]2, [Ru(COD)Cl2]n (COD=1,5-cyclooctadiene), Ru(PPh3)2(CO)2Cl2 and Ru(PPh3)3(CO)H2 for the hydrosilylation of HSi(R)x(OR)3-x (x=0-2) with an olefinic halide such as allyl chloride.
EP 0403706 A2 describes the use of Ru complexes having at least one tertiary phosphine ligand, for example Ru(CO)3 (PPh3)2, RuCl2(PPh3)2, Ru(H)(Cl)(PPh3)3, Ru(PPh3)4H2 and Ru(CH2═CH2)(PPh3)3, as catalysts for the hydro-silylation of allylamines by means of SiH-functional silanes.
U.S. Pat. No. 5,248,802 describes the hydrolysilylation of trichlorosilane with olefinic nitriles, e.g. acrylo-nitrile, in the presence of Ru-halogen or Ru-phosphine compounds such as RuCl3, RuBr3, RuI3, Ru(CO)3(PPh3)2, RuCl2 (PPh3)3, Ru(H)(Cl)(PPh3)3, RuH2(PPh3)4, Ru(CH2═CH2)(PPh3)3 and RuCl2(CO)2(PPh3)2.
Finally, DE 2810032 A1 describes the hydrosilylation of dichlorosilane with olefins in the presence of Ru complexes such as RuCl2(PPh3)3, Ru(H)(Cl)(PPh3)3, RuH3(PPh3)3[Si(OMe)3], RuH3(PPh3)3[Si(OMe)2Ph] and RuH2(PPh3)4.
However, these catalysts are generally significantly inferior to the customary Pt catalysts with respect to reactivity and selectivity. The rate and selectivity of the non-Pt catalysts used hitherto for hydrosilylation are generally not satisfactory, particularly for the crosslinking of polysiloxanes by means of a hydrosilylation reaction.
Very active Ru catalysts for hydrosilylation, in particular for the crosslinking of polysiloxanes, have also been described in DE 102006017588 A1. However, these very active catalysts have the disadvantage of total or partial incompatibility with polysiloxanes and a hydrosilylation selectivity which is significantly below that of customary Pt hydrosilylation catalysts, for example the “Karstedt” catalyst. The compatibility with polysiloxanes can be increased, for example, by introduction of “silicophilic” ligands, as described, for example, in DE 102006017594 A1 by way of η6-arene-Ru complexes. Despite the very good solubility of these catalysts in polysiloxanes, the activity and selectivity resulting from this class of catalyst in the crosslinking of polysiloxanes is still not always satisfactory.